1. Field
This invention relates to cyanoacrylate-containing compositions that include, in addition to the cyanoacrylate component, an anhydride and a maleimide-, itaconimide-, or nadimide-containing compound. Cured products of the inventive cyanoacrylate compositions demonstrate improved humidity and/or heat resistance.
2. Brief Description of Related Technology
Cyanoacrylate adhesive compositions are well known, and widely used as quick setting, instant adhesives with a wide variety of uses. See H. V. Coover, D. W. Dreifus and J. T. O'Connor, “Cyanoacrylate Adhesives” in Handbook of Adhesives, 27, 463-77, I. Skeist, ed., Van Nostrand Reinhold, New York, 3rd ed. (1990). See also G. H. Millet, “Cyanoacrylate Adhesives” in Structural Adhesives: Chemistry and Technology, S. R. Hartshorn, ed., Plenun Press, New York, p. 249-307 (1986).
U.S. Pat. No. 5,288,794 (Attarwala) is directed to an improved cyanoacrylate monomer adhesive formulation, where an effective amount, for enhancing the thermal resistance of the polymerized adhesive, of a mono, poly or hetero aromatic compound characterized by at least three substitutions on an aromatic ring thereof, two or more of the substitutions being electron withdrawing groups, is provided. Examples of the aromatic compound are given as 2,4-dinitrofluorobenzene; 2,4-dinitrochlorobenzene; 2,4-difluoronitrobenzene; 3,5-dinitromaleimide-, itaconimide-, or nadimide-containing compound; 2-chloro-3,5-dinitromaleimide-, itaconimide-, or nadimide-containing compound; 4,4′-difluoro-3,3′-dinitrophenyl sulfone; pentafluoronitrobenzene; pentafluoromaleimide-, itaconimide-, or nadimide-containing compound; α,α,α-2-tetrafluoro-p-tolunitrile and tetrachloroterphthalonitrile.
Prior to the discovery in the '794 patent, numerous attempts have been made to improve the thermal stability of cyanoacrylate adhesive bonds.
For instance, U.S. Pat. No. 3,832,334 is directed to the addition of maleic anhydride, which is reported to produce cyanoacrylate adhesives having increased thermal resistance (when cured) while preserving fast cure speed.
U.S. Pat. No. 4,196,271 is directed to tri-, tetra- and higher carboxylic acids or their anhydrides, which are reported to be useful for improving heat resistance of cured cyanoacrylate adhesives.
U.S. Pat. No. 4,450,265 is directed to the use of phthalic anhydride to improve heat resistance of cyanoacrylate adhesives. More specifically, the '265 patent is directed to and claims an adhesive composition comprising a polymerizable constituent the major part of which comprises at least one ester of 2-cyanoacrylic acid, characterized in that the composition additionally comprises a proportion of phthalic anhydride effective for favorably influencing the strength and/or durability of adhesive bonds formed from the composition, under exposure to moisture or elevated temperature. The effective amount is reported as 0.1% to 5.0%, such as 0.3% to 0.7%, by weight of the composition. The '265 patent reports the superiority of phthalic anhydride over compositions where no additive was used, and where maleic anhydride was used (though less pronounced in the case of stainless steel lapshears than in those of aluminium).
U.S. Pat. No. 4,532,293 is directed to the use of benzephenonetetracarboxylic acid or its anhydride and is said to provide a superior heat resistance for cyanoacrylate adhesives.
U.S. Pat. No. 4,490,515 is directed to cyanoacrylate compositions containing certain maleimide or nadimide compounds to improve hot strength properties.
Notwithstanding the state of the art and the efforts to date to improve the heat resistance of cyanoacrylate compositions, there remains a long felt, yet unmet, need to provide such moisture and/or heat resistance to cured reaction products of such cyanoacrylate compositions, particularly without compromising other physical properties like fixture time, stability or color of the cyanoacrylate compositions themselves. Until now.